Add chocolate chips, sweetened condensed milk, and dash salt to an 8-cup microwave-safe glass measure and stir to blend. Microwave on high for 1 minute. Stir and microwave 1 minute more. Stir until chocolate chips are completely melted and a smooth mixture has formed.

Stir in any mix-ins you're using to personalize your fudge (including vanilla extract) and spoon into prepared baking dish. Cover and chill in refrigerator for at least 2 hours, or until firm. Pull foil out of baking dish so you can easily cut fudge into about 49 squares (cut 7 columns vertically, then horizontally).